Negative Effects of Sugar Alcohols
The primary negative effect of sugar alcohols is gastrointestinal disturbances, particularly diarrhea, which occurs most commonly in children and unaccustomed individuals. 1
What Are Sugar Alcohols?
Sugar alcohols (polyols) are sweeteners and bulking agents used in food manufacturing, particularly in sugar-free products. Common examples include:
- Erythritol
- Isomalt
- Lactitol
- Maltitol
- Mannitol
- Sorbitol
- Xylitol
- Hydrogenated starch hydrolysates
These substances are recognized as safe by the FDA and are either designated as food additives or Generally Recognized as Safe (GRAS) 1.
Gastrointestinal Effects
Primary Concern: Osmotic Diarrhea
The most significant negative effect of sugar alcohols is their potential to cause gastrointestinal disturbances:
- Mechanism: Sugar alcohols are incompletely digested in the small intestine, with varying amounts reaching the colon where they are fermented by bacteria 2, 3
- Result: This can create an osmotic effect in the intestines, drawing water into the bowel and potentially causing diarrhea 1, 2
- Severity varies by type: The severity of gastrointestinal disturbances decreases in the following order: mannitol > sorbitol > xylitol 4
Regulatory Recognition of Risk
The FDA requires warning labels for certain sugar alcohols:
- Products containing mannitol must include a warning that "excess consumption may have a laxative effect" if daily ingestion could reach 20g
- Products with sorbitol require similar warnings if consumption could reach 50g daily 1
Adaptation
Research shows that adaptation to sugar alcohols may occur over time:
- Enzyme induction in intestinal flora can improve tolerance with continued use 2
- No pathological changes occur in the intestinal mucosa with typical consumption 2
Tolerance Differences Between Sugar Alcohols
Not all sugar alcohols have the same likelihood of causing digestive issues:
- Erythritol has the best tolerance profile due to its smaller molecular weight and different configuration compared to other sugar alcohols 2
- Xylitol is generally better tolerated than hexitols (like sorbitol and mannitol) or disaccharide polyols (like maltitol, lactitol) 2
- Lactitol has a higher percentage of malabsorption in the small intestine (84%) compared to maltitol and isomalt (44% and 40% respectively) 3
Energy Value and Metabolism
Sugar alcohols are often used in "sugar-free" products, but they do provide calories:
- They contain approximately 2 calories/g on average (about half the calories of sucrose) 1
- The energy values vary: sorbitol (3.58 kcal/g), maltitol (3.50 kcal/g), and hydrogenated glucose syrups (3.11-3.54 kcal/g) 5
- When calculating carbohydrate content of foods containing sugar alcohols, subtraction of half the total grams of sugar alcohols from total carbohydrate content is recommended 1
Clinical Implications
- There is no evidence that typical consumption of sugar alcohols will significantly reduce glycemia, energy intake, or weight 1
- Sugar alcohols produce a lower postprandial glucose response than sucrose or glucose 1
- They can reduce the risk of dental caries 1
Practical Considerations
When consuming products with sugar alcohols:
- Start with small amounts to assess individual tolerance
- Be aware that combining multiple sugar alcohol-containing products can increase the likelihood of digestive issues
- Children may be more susceptible to the laxative effects 1
- The quantities required to cause diarrhea when used for dental purposes (such as in sugar-free gum) are typically not reached in normal consumption 4